U.S. patent number 6,764,081 [Application Number 10/028,932] was granted by the patent office on 2004-07-20 for supplemental seal for the chordal hinge seals in a gas turbine and methods of installation.
This patent grant is currently assigned to General Electric Company. Invention is credited to Mahmut Faruk Aksit, Ning Fang, Abdul-Azeez Mohammed-Fakir, Ahmad Safi, Srikanth Vedantam.
United States Patent |
6,764,081 |
Mohammed-Fakir , et
al. |
July 20, 2004 |
Supplemental seal for the chordal hinge seals in a gas turbine and
methods of installation
Abstract
In a gas turbine, a supplemental seal is provided between an
annular axially facing sealing surface of a nozzle support ring and
an annular axially opposed sealing surface formed by
circumferentially adjacent nozzle segments. Each segment carries an
inner rail mounting a chordal hinge seal which engages the sealing
surface of the nozzle support ring. That seal is supplemented by a
generally arcuate V-shaped seal between the sealing surfaces which
opens radially inwardly toward a high pressure leakage path past
the chordal hinge seal. The supplemental seal is initially
compressed and maintained in a compressed condition during
installation by application of a solder. At operating temperature,
the solder melts away, releasing the supplemental seal to seal
between the nozzle support ring and nozzle segments.
Inventors: |
Mohammed-Fakir; Abdul-Azeez
(Schenectady, NY), Aksit; Mahmut Faruk (Istanbul,
TR), Safi; Ahmad (Troy, NY), Vedantam;
Srikanth (Niskayuna, NY), Fang; Ning (West Chester,
OH) |
Assignee: |
General Electric Company
(Schenectady, NY)
|
Family
ID: |
21846293 |
Appl.
No.: |
10/028,932 |
Filed: |
December 28, 2001 |
Current U.S.
Class: |
277/637; 277/647;
277/652 |
Current CPC
Class: |
F01D
11/005 (20130101); F16J 15/0887 (20130101) |
Current International
Class: |
F01D
11/00 (20060101); F16J 15/08 (20060101); F16J
015/02 (); F01D 009/04 () |
Field of
Search: |
;277/637,642,641,647,652
;415/191,209.2 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Pickard; Alison K.
Attorney, Agent or Firm: Nixon & Vanderhye
Claims
What is claimed is:
1. A turbine comprising: a turbine nozzle support ring having a
generally axially facing first surface; a turbine nozzle segment
having at least one stator vane and including an inner band having
a second surface in axial opposition to said first surface; a
flexible seal between said first and second surfaces including a
seal body between high and low pressure regions on opposite sides
of the seal, said seal body including first and second portions in
opposition to one another and coupled to one another along
adjoining edges thereof; opposite edges of said first and second
portions being spaced from one another defining an opening into a
cavity in the seal body between said first and second portions,
said first and second portions being preloaded to bear against the
first and second surfaces, respectively, with said cavity opening
toward the high pressure region; said first and second portions
being initially compressed relative to one another such that at
least one of said opposite edges is spaced from one of said first
and second surfaces and means for releasably retaining said first
and second portions in a state of compression with said one
opposite edge spaced from said one of said first and second
surfaces, said means enabling release of said compressed portions
in response to turbine operating conditions.
2. A turbine according to claim 1 wherein said seal is in the form
of an arcuate segment.
3. A turbine according to claim 1 wherein said seal body includes a
stem extending from one of said edges bearing against one of the
first and second surfaces and extending along said one surface,
said stem being secured to said one surface.
4. A turbine according to claim 1 wherein said nozzle segment
includes a generally radially inwardly extending inner rail having
a generally axially extending projection engageable with said first
surface to form a second seal therewith.
5. A turbine according to claim 4 wherein said projection extends
in a chord-wise direction relative to an axis of the turbine
rotor.
6. A turbine comprising: a turbine nozzle support ring having a
generally axially facing first surface; a turbine nozzle segment
having at least one stator vane and including an inner band having
a second surface in axial opposition to said first surface; a
flexible seal between said first and second surfaces including a
seal body between high and low pressure regions on opposite sides
of the seal, said seal body including first and second portions in
opposition to one another and coupled to one another along
adjoining edges thereof; opposite edges of said first and second
portions being spaced from one another defining an opening into a
cavity in the seal body between said first and second portions,
said first and second portions being preloaded to bear against the
first and second surfaces, respectively, with said cavity opening
toward the high pressure region; wherein said first and second
portions are initially compressed relative to one another such that
at least one of said opposite edges is spaced from one of said
first and second surfaces and means for maintaining said first and
second portions in a state of compression; and wherein said means
includes a solder applied to said first and second portions and
releasable in response to turbine operating temperatures to enable
the first and second portions for displacement from their
compressed state to their preloaded state with the edges engageable
against the first and second surfaces, respectively, to form a seal
therebetween.
7. A gas turbine comprising: a turbine nozzle support ring having a
generally axially facing first surface; a turbine nozzle segment
having at least one stator vane and including an inner band having
a second surface in axial opposition to said first surface; a
flexible seal between said first and second surfaces including a
seal body between high and low pressure regions on opposite sides
of the seal, said seal body including first and second portions in
opposition to one another and coupled to one another along
adjoining edges thereof; said seal body including a stem extending
from said second seal portion and bearing against one of said first
and second surfaces, an overlay of material along at least said
first and second portions and at least portions of said stem
maintaining said first and second portions in a state of
compression generally against said stem portion, said material
being releasable from said portions to enable said first and second
portions to resiliently move away from one another and from said
stem to engage a distal edge of said first portion against another
of said first and second surfaces, respectively.
8. A gas turbine according to claim 7 wherein said first and second
portions define a cavity therebetween in the seal body opening into
the high pressure region.
9. A gas turbine according to claim 7 wherein said material is
releasable at turbine operating conditions to enable displacement
of the first and second portions from their compressed state to
sealingly engage the distal edge against said another of said first
and second surfaces.
10. A gas turbine according to claim 9 wherein said stem is secured
to said nozzle segment and one of said first and second portions
has a free edge engageable against said first surface of said
nozzle support ring.
11. A gas turbine according to claim 7 wherein said nozzle segment
includes a generally radially inwardly extending inner rail having
a generally axially extending projection engageable with said first
surface to form a second seal therewith.
12. A gas turbine according to claim 11 wherein said projection
extends in a chord-wise direction relative to an axis of the
turbine rotor.
13. A gas turbine according to claim 7 wherein said stem is formed
of sheet material having a thickness greater than the thickness of
sheet material forming said first and second portions.
14. A gas turbine according to claim 7 wherein said seal is arcuate
about the axes of the turbine.
15. A method of forming a seal in a gas turbine having a nozzle
support ring including a first axially facing sealing surface and
an annular array of nozzles formed of a plurality of nozzle
segments each having an inner band and a second, generally axially
facing sealing surface in general axial opposition to said first
surface comprising the steps of: providing a flexible seal having
first and second portions in opposition to one another and
connected to one another along adjoining edges thereof; compressing
the first and second portions toward one another to form a
compressed seal; maintaining the compressed seal with a distal edge
of said first portion remote from the adjoining edges spaced from
another of said first and second surfaces; securing the compressed
seal to one of said first and second surfaces and between said
surfaces; and releasing the first and second portions of the
compressed seal to enable the distal edge to move toward and engage
said another of said first and second surfaces in response to
turbine operating conditions.
16. A method according to claim 15 including providing the seal
with a stem secured to said second portion and securing said stem
to said one of said first and second surfaces.
17. A method of forming a seal in a gas turbine having a nozzle
support ring including a first axially facing sealing surface and
an annular array of nozzles formed of a plurality of nozzle
segments each having an inner band and a second, generally axially
facing sealing surface in general axial opposition to said first
surface comprising the steps of: providing a flexible seal having
first and second portions in opposition to one another and
connected to one another along adjoining edges thereof; compressing
the first and second portions toward one another to form a
compressed seal; securing the compressed seal to one of said first
and second surfaces and between said surfaces; releasing the first
and second portions of the compressed seal to enable a distal edge
of said first portion remote from the adjoining edges to engage
another of said first and second surfaces; and enveloping the first
and second portions in a material maintaining the first and second
portions under compression and enabling the material when disposed
between said first and second surfaces for release of the first and
second portions and displacement of the first portion for sealing
engagement against said another of said first and second
surfaces.
18. A method according to claim 17 including providing the seal
with a stem secured to said second portion and securing said stem
to said second surface, enveloping the first and second portions
and a portion of said stem with a solder material which melts at
turbine operating conditions.
Description
BACKGROUND OF THE INVENTION
The present invention relates to seals in a gas turbine for
supplementing the chordal hinge seals between turbine nozzles and a
turbine nozzle support ring and particularly relates to
supplementary seals for substantially minimizing or eliminating
leakage losses past the chordal hinge seals.
In a gas turbine, hot gases of combustion flow from combustors
through first-stage nozzles and buckets and through the nozzles and
buckets of follow-on turbine stages. The first-stage nozzles
typically include an annular array or assemblage of cast nozzle
segments each containing one or more nozzle stator vanes per
segment. Each first-stage nozzle segment also includes inner and
outer band portions spaced radially from one another. Upon assembly
of the nozzle segments, the stator vanes are circumferentially
spaced from one another to form an annular array thereof between
annular inner and outer bands. A nozzle retaining ring coupled to
the outer band of the first-stage nozzles supports the first-stage
nozzles in the gas flow path of the turbine. An annular nozzle
support ring, preferably split at a horizontal midline, is engaged
by the inner band and supports the first-stage nozzles against
axial movement.
In an exemplary arrangement, eighteen cast segments are provided
with two vanes per segment. The annular array of segments are
sealed one to the other along adjoining circumferential edges by
side seals. The side seals seal between a high pressure region
radially inwardly of the inner band, i.e., compressor discharge air
at high pressure, and the hot gases of combustion in the hot gas
flow path which are at a lower pressure.
Chordal hinge seals are used to seal between the inner band of the
first-stage nozzles and an axially facing surface of the nozzle
support ring. Each chordal hinge seal includes an axial projection
which extends linearly along a chord line of the inner band portion
of each nozzle segment. Particularly, the chordal hinge seal
extends along an inner rail of each segment and which rail extends
radially inwardly of the inner band portion. The chordal hinge seal
projection lies in sealing engagement with the axially opposite
facing sealing surface of the nozzle support ring.
During operation and/or repair of the first-stage nozzle, it has
been found that warpage can leave gaps between the chordal hinge
seals and the sealing surface of the nozzle support ring. These
gaps enable leakage past the chordal hinge seals from the high
pressure area radially within the annular inner band into the hot
gas flow path. That is, the chordal hinge seals are inadequate to
prevent leakage flow as the chordal hinge seal projections lose
contact with the sealing surface of the nozzle support ring.
Consequently, there is a need for a supplemental seal at the
interface of the first-stage nozzles and nozzle support ring to
minimize or eliminate the leakage flow past the chordal hinge
seals.
BRIEF DESCRIPTION OF THE INVENTION
In accordance with a preferred embodiment of the present invention,
there is provided a supplemental seal between the first-stage
nozzles and the nozzle support ring which eliminates or minimizes
leakage past the chordal hinge seals and which is readily and
easily installed without reconfiguration of the first-stage nozzles
or nozzle support ring. The supplemental seal comprises a generally
V-shaped seal for disposition between the axially facing first
surface of the nozzle support ring and an axially facing second
surface of a turbine nozzle segment. Particularly, the nozzle
segment includes a radially inwardly projecting inner rail mounting
the chordal seal which engages the first surface of the nozzle
support ring. The inner rail also has a shallow recess radially
outwardly of the projection forming the chordal hinge seal. The
supplemental seal is disposed between the first and second axially
registering surfaces for sealing engagement therebetween.
More particularly, the supplemental seal extends arcuately between
the first and second sealing surfaces and includes a stem enabling
the supplemental seal to be secured to the sealing surface of the
inner rail, for example, by bolting. The V-shaped portion of the
supplemental seal faces inwardly and in operation, a free edge of
the V-shaped seal bears against the first sealing surface. The
opposite edge is joined to an edge of the stem and forms a sealing
surface with the second annular surface. Thus, the V-shape opens
radially inwardly in registration with the high pressure region in
the event of leakage past the chordal hinge seal. Any high pressure
leakage flexes or biases the seal into engagement to seal between
the opposite first and second annular surfaces. The circumferential
extent of the supplemental seal is preferably coincident with the
circumferential extent of the nozzle segment.
A feature of the present invention resides in initially compressing
and maintaining the seal compressed in a substantially arcuate
planar form prior to assembly and upon initial assembly, into the
machine. To accomplish this, the legs of the V-shaped seal are
compressed against the stem and a material, preferably a solder, is
applied to maintain the V-shaped seal in a compressed condition.
The soldered compressed seal forms essentially a solid block or
seal piece which facilitates handling, avoids exposed sharp edges
and affords a sturdiness and robustness to the seal during handling
and installation. The supplemental seal is installed by bolting in
its compressed condition to the second annular surface along the
shallow recess of the inner rail. When the turbine is brought up to
operating conditions, e.g., when the turbine temperature exceeds
that of the melting temperature of the solder, the solder melts
away, releasing the V-shaped portion of the seal from its
compressed state into an expanded state and into engagement with
the opposite first and second sealing surfaces of the nozzle
support ring and the inner rail, respectively.
In a preferred embodiment according to the present invention, there
is provided a turbine comprising a turbine nozzle support ring
having a generally axially facing first surface, a turbine nozzle
segment having at least one stator vane and including an inner band
having a second surface in axial opposition to the first surface, a
flexible seal between the first and second surfaces including a
seal body between high and low pressure regions on opposite sides
of the seal, the seal body including first and second portions in
opposition to one another and coupled to one another along
adjoining edges thereof, opposite edges of the first and second
portions being spaced from one another defining an opening into a
cavity in the seal body between the first and second portions, the
first and second portions being preloaded to bear against the first
and second surfaces, respectively, with the cavity opening toward
the high pressure region.
In a further preferred embodiment according to the present
invention, there is provided a gas turbine comprising a turbine
nozzle support ring having a generally axially facing first
surface, a turbine nozzle segment having at least one stator vane
and including an inner band having a second surface in axial
opposition to the first surface, a flexible seal between the first
and second surfaces including a seal body between high and low
pressure regions on opposite sides of the seal, the seal body
including first and second portions in opposition to one another
and coupled to one another along adjoining edges thereof, the seal
body including a stem extending from the second seal portion and
bearing against one of the first and second surfaces, an overlay of
material along at least the first and second portions and at least
portions of the stem maintaining the first and second portions in a
state of compression generally against the stem portion, the
material being releasable from the portions to enable the first and
second portions to resiliently move away from one another and from
the stem to engage a distal edge of the first portion against
another of the first and second surfaces, respectively.
In a further preferred embodiment according to the present
invention, there is provided a method of forming a seal in a gas
turbine having a nozzle support ring including a first axially
facing sealing surface and an annular array of nozzles formed of a
plurality of nozzle segments each having an inner band and a
second, generally axially facing sealing surface in general axial
opposition to the first surface comprising the steps of providing a
flexible seal having first and second portions in opposition to one
another and connected to one another along adjoining edges thereof,
compressing the first and second portions toward one another to
form a compressed seal, securing the compressed seal to one of the
first and second surfaces and between the surfaces and releasing
the first and second portions of the compressed seal to enable a
distal edge of the first portion remote from the adjoining edges to
engage another of the first and second surfaces.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a fragmentary schematic side elevational view of a
portion of a gas turbine;
FIG. 2 is an enlarged fragmentary cross-sectional view illustrating
a conventional chordal seal hinge;
FIG. 3 is a fragmentary perspective view illustrating a portion of
a conventional chordal hinge seal along an inner rail of a nozzle
segment;
FIG. 4 is a fragmentary perspective view with parts in
cross-section illustrating the conventional chordal hinge seal in
sealing engagement with a nozzle support ring of the gas
turbine;
FIG. 5 is an enlarged cross-sectional view of a supplemental seal
disposed between sealing surfaces of the annular support ring and
the inner rail;
FIG. 6 is an enlarged cross-sectional view of the supplemental
seal; and
FIG. 7 is a fragmentary perspective view illustrating schematically
the compression of the supplemental seal and its retention in a
compressed state prior to and during installation.
DETAILED DESCRIPTION OF THE INVENTION
Referring now to FIG. 1, there is illustrated a representative
example of a turbine section of a gas turbine, generally designated
10. Turbine 10 receives hot gases of combustion from an annular
array of combustors, not shown, which transmit the hot gases
through a transition piece 12 for flow along an annular hot gas
path 14. Turbine stages are disposed along the hot gas path 14.
Each stage comprises a plurality of circumferentially spaced
buckets mounted on and forming part of the turbine rotor and a
plurality of circumferentially spaced stator vanes forming an
annular array of nozzles. For example, the first stage includes a
plurality of circumferentially-spaced buckets 16 mounted on a
first-stage rotor wheel 18 and a plurality of
circumferentially-spaced stator vanes 20. Similarly, the second
stage includes a plurality of buckets 22 mounted on a rotor wheel
24 and a plurality of circumferentially-spaced stator vanes 26.
Additional stages may be provided, for example, a third stage
comprised of a plurality of circumferentially-spaced buckets 28
mounted on a third-stage rotor wheel 30 and a plurality of
circumferentially-spaced stator vanes 32. It will be appreciated
that the stator vanes 20, 26 and 32 are mounted on and fixed to a
turbine casing, while the buckets 16, 22 and 28 and wheels 18, 24
and 30 form part of the turbine rotor. Between the rotor wheels are
spacers 34 and 36 which also form part of the turbine rotor. It
will be appreciated that compressor discharge air is located in a
region 37 disposed radially inwardly of the first stage and that
such air in region 37 is at a higher pressure than the pressure of
the hot gases flowing along the hot gas path 14.
Referring to the first stage of the turbine, the stator vanes 20
forming the first-stage nozzles are disposed between inner and
outer bands 38 and 40, respectively, supported from the turbine
casing. As noted above, the nozzles of the first stage are formed
of a plurality of nozzle segments 41 (FIG. 3) each mounting one,
preferably two, stator vanes extending between inner and outer band
portions and arranged in an annular array of segments. A nozzle
retaining ring 42 connected to the turbine casing is coupled to the
outer band and secures the first-stage nozzle. A nozzle support
ring 44 radially inwardly of the inner band 38 of the first-stage
nozzles engages the inner band 38. Particularly, the interface
between the inner band 38 and the nozzle support ring 44 includes
an inner rail 52 (FIG. 2). The inner rail 52 includes a chord-wise,
linearly extending axial projection 48, generally and collectively
hereinafter referred to as a chordal hinge seal 46. Projection 48
extends along an axial facing surface 50 of the inner rail 52 which
forms an integral part of each nozzle segment and specifically the
inner band 38. The projection 48 engages a first annular surface 54
of the nozzle support ring 44. It will be appreciated that high
pressure compressor discharge air lies in the region 37 and lower
pressure hot gases flowing in the hot gas path 14 lie on the
opposite side of the seal 48. The chordal hinge seal 46 thus is
intended to seal against leakage from the high pressure region 37
into the lower pressure region of the hot gas path 14.
As noted previously, however, in operation, component parts of the
nozzles and nozzle support ring will tend to form leakage gaps
between the projection 48 and the surface 54 of the nozzle support
ring 44 whereby leakage flow may occur from the high pressure
region to the low pressure region. In order to minimize or prevent
leakage flow into the hot gas path 14, and in accordance with a
preferred embodiment of the present invention, there is provided a
supplemental seal for sealing between the first-stage nozzles and
the nozzle support ring 44. The supplemental seal, generally
designated 60, is disposed between the first sealing surface 54 of
the nozzle support ring 44 and the second sealing surface 50 of the
inner rail 52 of the inner band 38. As illustrated in FIG. 6, the
sealing surface 50 comprises a shallow recess along the axially
facing surface 62 of the inner rail 52. The supplemental seal 60 is
arcuate and has a circumferential extent corresponding to the
circumferential extent of the inner rail 52 of the nozzle
segment.
Supplemental flexible seal 60 includes a seal body 63 having first
and second arcuate sheet metal portions 64 and 66, respectively,
folded over one another to form a generally V-shaped configuration
opening radially inwardly upon installation in the turbine. As
illustrated in FIG. 6, the distal or free edge 65 of the first seal
portion 64 bears against the first annular sealing surface 54 of
the nozzle support ring 44. The second portion 66 of the generally
V-shaped supplemental seal 60 terminates along its edge bearing
against the second annular sealing surface 50 of the inner rail 52.
The edge of the second portion 66 is also connected to a stem 68.
The stem is formed of a sheet material thicker than the material
forming the V-shaped first and second portions 64 and 66,
respectively, of the supplemental seal 60. The seal 60 is
preferably formed of sheet metal. The stem 68 includes a number of
openings 69 whereby the stem can be secured to the surface 50 of
the inner rail 52, for example, by bolts. The supplemental seal
extends arcuately from edge to edge of each segment and is secured
to locate the V-shaped first and second portions 64 and 66,
respectively, between the sealing surfaces 54 and 50. It will be
appreciated that with the seal installed as illustrated, the
V-shaped seal body opens toward the chordal hinge seal and is thus
exposed to the high pressure in region 36 in the event of leakage
past the chordal hinge seal. The high pressure leakage flow
maintains the portions 64 and 66 of the V-shaped seal in engagement
against the opposed sealing surfaces.
To facilitate handling and installation of each supplemental seal,
the V-shaped portion of the seal body 63 including the stem 68 is
compressed, as illustrated in FIG. 7. While maintaining the seal in
a state of compression, the seal is coated with a solder 70 that
maintains the seal body 63 in a solid monolithic state. The thick
coating of solder 70 on the supplemental seal 60 enables safe
handling of the seal during installation, eliminates any sharp
edges along the seal by embedding such edges within the solder
material and renders the seal sturdy and robust during handling and
installation. After the supplemental seal is secured, e.g., by
bolting, to the inner rail 52 with the compressed portions 64 and
66 disposed between sealing surfaces 54 and 50, the solder, at
machine operating conditions, i.e., high temperatures, melts away,
releasing the seal from its monolithic compressed state. This
enables the portions 64 and 66 to expand away from one another into
engagement with the surfaces 54 and 50, respectively. It will be
appreciated that the seal body is preloaded and thus the portions
64 and 66 expand toward their natural unbiased positions. An
alternative material for maintaining the supplemental seal in a
compressed condition comprises wax.
It will also be appreciated that the supplemental seal, instead of
being formed in circumferential lengths corresponding to the
circumferential length of each nozzle segment along its inner rail,
may be formed in greater arcuate lengths. In that manner, the
supplemental seals may overlap the side seals between adjacent
nozzle segments, in effect providing supplemental seals for the
side seals.
While the invention has been described in connection with what is
presently considered to be the most practical and preferred
embodiment, it is to be understood that the invention is not to be
limited to the disclosed embodiment, but on the contrary, is
intended to cover various modifications and equivalent arrangements
included within the spirit and scope of the appended claims.
* * * * *